Mechanical lash adjuster



Jann., 28, 1958 MMIII; nunk S. OLDBERG MECHANICAL LASH ADJUSTER Filed Oct. 10, 1955 .I N VEN TOR. 52m/y Uwene l Arrange-ys Unite rates MECHANICAL LASH ADJU STER Application October 10, 1955, Serial No. 539,357

16 Claims. (Cl. 12S-90) This invention relates to lash adjusters of the kind used for automatic length adjustment purposes in linkages and particularly in linkages for actuating the valves of an internal combustion engine. The lash adjuster of the present invention is of the mechanical type as distinguished from lash adjusters of the hydraulic type.

An object of the invention is to provide a mechanical lash adjuster of a novel form comprising a relatively small number of parts and capable of functioning in a practical and eiicient manner throughout a prolonged period of service, and which can be readily incorporated in a compact and self-contained unit such as in a valve tappet.

A Another object is to provide a mechanical lash adjuster comprising a pair of relatively movable parts adapted to be subjected to reciprocative loading, and a length adjusting means operably connecting such parts and responsive to variations in the applied load for automatically varying the effective length of the adjuster.

A further object is to provide such a mechanical lash adjuster in which one of the parts of said pair has inclined-plane bearing means thereon engaged by relatively movable members of the length-adjusting means, and in which variations in the applied load are eiective on such relatively movable members through oppositely sloping bearing means, such that controlled relative movement between said members automatically causes variation in the effective length of the adjuster.

j Still another object is to provide a mechanical lash adjuster of the kind above indicated, in which the relative movement between said members is controlled, at least in part, by resilient means eifective between those members to transmit force therebetween.

l Yet another object is to provide a novel form of me chanical lash adjuster comprising relatively movable substantially coaxial parts adapted to be subjected to reciprocative loading and one of which parts is threaded, and a pair of members having threaded engagement with such one part and also having rotative drive connection with the other of said parts through oppositely sloping spline elements, such that relative rotation between said members in response to variation in the applied load automatically causes variation in the eiective length of the adjuster.

As still another object, this invention provides such a mechanical lash adjuster in which relative rotation between the pair of members is controlled by torsion spring means, including a double-acting cantilever spring means effective between such pair of members.

The invention can be further briey summarized as consisting in certain novel combinations and arrangements of parts hereinafter described and particularly setV out in the claims hereof.

In the accompanying sheet of drawings forming a part of this specification:

atent- O 1 70 Fig. 1 is an axial sectional View taken through a mehanical lash adjuster embodying the present inventiong.

Fig. 2 is an axially exploded View of the lash adjuster' of Fig. 1;

Fig. 3 is a top plan view of the inner nut member of the lash adjuster, such view being taken as indicated by the line 3-3 of Fig. 2;

Fig. 4 is a bottom plan view of the outer nut member of the lash adjuster, such view being taken as indicated. by line 4 4 of Fig. 2;- and Fig. 5 is a view of a diagrammatic form illustrating the functioning of the lash adjuster and representing an analog thereof.

As one practical embodiment of this invention, the drawing shows a mechanical lash adjuster 10 in the form of a tappet adapted for use in an internal combustion engine for transmitting reciprocative loads between an engine valve and a valve actuating cam. Such a tappet is usually mounted in a hollow guide bearing for axial sliding movement therein.

The lash adjuster 10 comprises, in general, a pair of substantially coaxially disposed parts 11 and 12 of which the outer part 11 forms a housing member having an axial chamber 13 therein and the part 12 is a stem disposed in a substantially coaxial telescoping relation in such outer part. The lash adjuster 10 also comprises a pair of mem-- bers 15 and 16 forming an operative connection between the coaxial parts 11 and 12.

The outer part 11 is preferably a one-piece metal member and is of a shape suitable for a tappet body. As here shown, the part 11 has a cylindrical outer surface 17 and a transverse end wall 18 forming the bottom of the chamber 13 and whose lower surface 18a is engageable by the valve actuating cam. The part 11 is provided with an internal helical thread 19, of either a single or multipley pitch characteristic, and which extends along the chatnber 13 from the end wall 18 to a point adjacent the end opening 20 of the upper end of this part. The helical thread 19 provides an inclined-plane bearing means on the part 11. Adjacent the end opening 20 the part 11 is also provided with an internal annular locking groove 21.

The stem comprising the inner part 12 is provided adjacent the lower and upper ends thereof with groups of spline elements 23 and 24. The spline elements 23 andl 24 are formed on end portions of the part 12, which are connected by an intermediate stem portion 25 of a relatively smaller transverse dimension than the root diameter of the spline elements. An important characteristic of the part 12 is that the spline elements 23 and 24, although extending in the general direction of the axis of this part, are oppositely inclined so as to define oppositely sloping bearing means or wedge means on this part. As here shown, the spline elements 23 are inclined so as to have a left-hand pitch characteristic and the oppositely inclined spline elements 24 have a right-hand pitch characteristic.

The inner member 15 is a nut member having an external helical thread 27 thereon which engages the internal thread 19 of the outer part 11. The external thread 27 is of either a single or multiple pitch characteristic, depending upon the characteristic of the thread 19. The nut member 15 has a central axial opening 28 into which the lower end of the inner part 12 extends and carries an annular group of internal spline elements 29 surrounding such axial opening and having meshed engagement with the spline elements 23.

The outer member 16 is also a nut member having an external helical thread 31 thereon engaging the internal thread 19 of the part 11 and which external thread is of the same pitch characteristic as the internal thread. The nut member 16 has a central axial opening 32 through which the upper end of the inner part 12 extends, such that the upper end of the inner partis exa.-

3 posed for engagement by the lower end of the valve stem, or with a part or member interposedr between the lash adjuster and such valve stern.

TheY outer nut member 16 carries an annular group of internal spline elements 33 which are disposed, around the central opening 32. and have meshed engagement with the spline elements 27,4 of the inner part 12. Since the spline elements 24 of the part 12 have a right-hand pitch characteristic, the spline elements 33 of the nut member 16 likewise have a right-hand( pitch characteristie.

The external threads 27 and 31; off the nutmembers and 16 constitute follower means which are slidable along the inclined-plane bearing means provided on the part 11 by the helical thread 19. The groups of righthand and left-hand spline elements 23 and, 24 constitute oppositely sloping bearing means on the part 12, while' the spline groups 29 and 33 ofthe nut members 15 and 16r constitute other follower means coacting with such oppositely sloping bearing means.

For a purpose which will be further explained hereinafter, a coupling in the form of a resilient connecting means is provided between the nut members 15. and 16 for controlling relative rotation therebetween'. This resilient connecting means is here shown as comprising cantilever arm projections or torsion spring elements 35r and 36. carried by the inner nut member 15 and extending axially upwardly 'therefrom into recesses 37 and 38 of the outer nut member 16'. The axial projectionsV 35 and 36r of the nut member 15 are here shown` as being formedV as integral portions of this member and con-V stitute` relatively stiff, but torsionally yieldable, cantilever spring elements. The spring elements 35 and 36 are annularly spaced about the common axis 39 of the.

lash adjuster 10 and, in this instance, only two such spring elements are provided and are in a substantially ing inclined side faces 40, and the recesses 37 and 38 likewise have an axially outwardly converging shape defined by pairs of opposed inclined side faces 41. The

slopev angle ofthe side faces 40 of the spring projectionsv 3,5I and 3 6 is` somewhat smaller than the slope angle of' the inclined side faces 41'oft the recesses 37 and 38,` such that the springyprojections have a relatively loose engagement in the recesses with an intervening clearance space 42,' betweenY their adjacent inclinedV sidefaces;Y

`'I'he lashadjuster 10; also includes a spring 4.4Y located in thechamber 13 andieffective on the inner nut member 1 5;l Thev spring 44 is here shown as being aA torsion spring having itsinner end connected with the part 11 by means of a spring retainer 45,. The spring retainer 45 can be of any appropriate character and is here shown-as beinga cup-shaped sheet metal member having an annular ange 46threadedly engaged'with the internal thread 19. The lower end of the spring 44 extends into the axial recess-47 of the retainer 45 and is connected with the retainer by having asubstantially radial arm'48 engaged-v in an opening 49 in theside wall of the retainer. The-upper-fendof the spring44 extends-into an axial recessl 50dened in `the lower end of the inner nut member 15 by a'depending axial sleeve portion 51 of thelatter. upperrend= ofi the spring is connected with this nut member by-havingra substantiallyfradial arm 52 engaged inan opening. 53 provided in thesleeveportion 51.

InI the... assembling of 'the .above-described componentsy spring-rtmtheretaner. 45! and: advance theretainerf along The spring projections 35 and 36 are ofa tapered shape having axially outwardly convergthe thread 19 part-way into the chamber 13. The nut members 15 and 16 are applied to the spline groups 23 and 24 of the inner part 12 with the spring projections 35 and 36 engaged in the recesses 37 and 38. The inner nut member 15 is then connected to the outer end of the spring 44, after which the axial group comprising the retainer 45, the spring 44, the. part 12 and the nut mem- Vbers 15 and 1 6` is advanced into the. chamber 13 by ros 54 engaged inthe internal groove 21.

When the lash adjuster 10j is. inl an unloaded condition,I such asthat in which it is shown in Fig. l of thedraw. ing, the annular shoulder 55 of thenut member 1.6is in, engagement with the snap ring 54. When the lashE ad-Y juster 10 is assembled in a valve actuating linkage on mechanism, the nut members 15 and 16. are advanced inwardly along the internal thread 19 of the part 11l ,to thereby load, orv increasethe loading of, the torsion springA 44 such that a suitable clearance will` exist between the annular shoulder 55 of the outer nut member 16 and.' the; snap ringf54`., The expansive.l action of' the valvef spring of' the valve mechanism with which the lash ad.,-L justerv 10 is associated, imposes an initial load on the lash adjuster which normally balances the expansive action' of' the torsion spring 44 when the engine valve. is seated to thereby preventthe outer nut' member 1,6', from being moved into engagement with the snapring 54,.V

In the use of the mechanical lash adjuster 10 in a.v valve actuating mechanism of an internal combustion en? gine, it is desirable that the lash adjuster be subjected.l

` to an automatic shortening action during a portion ofiI the valve operating cycle for the purpose of introducingl intov the valve actuatingmechanism what can be con?` veniently termed lift loss. Such liftloss in themeclif anism insures proper seating of the valve during, the. closing movementl of the latter. It is also desirable that". the lift loss thus-introduced into the valve actuating mech-A anism be automatically removed therefrom during another portion of the valve operating cycle so as to elim,

inatelooseness and noise-at the beginning ofthenext subsequent valve operating cycle.

TheV operation of' the lash adjuster 10, duringwhichL the above-mentioned desired automatick shortening and' lengthening functions are obtained in the valve operatlng cycle, will be` presently described in detail but be-, fore proceeding with such description reference can adi vantageously bei madek to the diagrammatic view orianalog 102' of Fig. 5. rln this analog 10, a` pair o f; lower andl upper par-ts 11aV and 172a correspond respectivelyA with the Yabove-described relatively movable outer and inner-:parts 1-1- and-121 of the lash adjuster 10; Similarly, a pair of laterally spaced membersV 1,5*L and 16a4 disposed between the parts 11a and 12S' correspond respectively with the inner and outer nut members 1 5 and 1t?.V spring:57fdisposed between and connectedwith the members 15@ and 16?# corresponds witlr the double-acting cantilever spring means formed' by the arms 35 and 36. Similarly, aspringSS` extending between andi connected with the part 11a andI the member 15a corresponds'with the torsion, spring 44: A i

In they analogfll). the lower. part 11a has an inclinedplanebearing.V means 59 thereon corresponding` with` the internal thread 19 of the outer part' 11. The'inc-linationf of. the.. inclined. bearing Surface 5 9 is represented by the angle 6l) and corresponds substantially with the pitchI V are slidable on the beating surface 59, such that movement of these members along this bearing surface in uphill and downhill directions are comparable with uphill and downhill movements of the nut members and 16 along the internal thread 19.

The lower member 11a of the analog 10a is shown as having an arm portion 61 at the low end thereof and the spring 58 is shown as having its ends attached respectively to the arm 61 and to the member 15a, such that a preloaded condition of this spring will inuence the movements of the member 15a along the inclined bearing surface 59. The spring 57 is shown in the analog as being located between the members 15a and 16a and as having its opposite ends connected to these members, such that it can serve as a double-acting spring and such that relative movement between these members along the inclined bearing surface 59 will cause loading or unloading of this spring for influencing or controlling such movements of these members.

The upper part 12a of the analog has oppositely sloping bearing surfaces 63 and 64 thereon with which oppositely sloping bearing surfaces 65 and 66 on the upper ends of the members 15a and 16a have sliding engagement. The slope angle 67 of these sloping bearing surfaces corresponds substantially with the slope angle of the oppositely inclined elements of the spline groups 23 and 24 of the lash adjuster 10.

In the operation of the lash adjuster 10, an increase in the load applied thereto by the lifting action of the valve actuating cam causes a tendency for the inner part 12 to be moved axially downwardly relative to the outer part 11. Under the influence of this compressive load the oppositely inclined spline groups 23 and 24 are effective on the inner and outer nut members 15 and 16 to produce relative rotation between these nut members, causing the spring arms and 36 to be subjected to load by a torsional exing thereof. During this torsional loading of the spring arms 35 and 36 by relative movement between the nut members 15 and 16, the outer nut member 16 remains relatively stationary while the inner nut member 15 is rotated in a clockwise direction and thereby advanced downwardly along the internal thread 19. During this relative rotary movement between the nut members 15 and 16, the spring arms 35 and 36 engage against the inclined side walls 41 of the recesses 37 and 33 on one side of the latter and are thereby deflected or sprung in a direction circumferentially of the device such that these spring arms are subjected to a torsional loading.

As the load imposed on the lash adjuster 16 is decreased during the downward movement of the valve actuating cam, the torque stored in the torsionally deflected arms 35 and 36 is relieved and is expended by causing relative rotation between the nut members 15 and 16 in a direction to produce shortening of the effective length of the lash adjuster 10, thereby introducing the above-mentioned lift loss into the valve actuating mechanism for insuring proper seating of the valve. During this expenditure of stored torque by the spring arms 35 and 36, the inner nut member 15 remains relatively stationary and the outer nut member 16 is rotated in a clockwise direction and thereby moved downwardly along the internal thread 19 of the part 11. During this downward movement of the outer nut member 16 the inner part 12 moves in the same direction with this nut member, thereby decreasing the length of the lash adjuster.

VThe continued downward movement of the valve actuating cam after the valve has reached its seated position, causes the load on the lash adjuster 10 to be further decreased to substantially the value of the initial loading of the lash adjuster and, if clearance develops in the valve actuating linkage, the condition will be such that the load has been substantially entirely removed from the lash adjuster. The presence of such clearance or lash in the valve actuating mechanism permits the spring 44 to move the nut members 15 and 16 outwardly along th internal thread 19, thereby also moving the inner part 12 in the same outward axial direction into engagement with the adjacent member of the valve actuating mech-2 anism. This outward axial movement of the inner part 12 lengthens the lash adjuster 10 and removes the lift loss from the valve actuating mechanism.

If the valve operating cycle is performed without any lash or clearance being immediately developed in the' mechanism then, of course, the spring 44 does not produce any such outward movement of the nut members 15 and 16 along the internal thread 19 for lengthening the device until some lash or clearance is actually developed and which may not occur until one or more subsequent valve operating cycles have been performed.

The reason why the above-explained relative movements between the nut members 15 and 16 actually take place under the control of the spring arms 35 and 3,6, can be further explained by reference to the analog 10a of Fig. 5. From this analog and the relation of the springs and sliding surfaces thereof, it will be seen that when the compressive load being applied to the lower and upper parts 11a and 12a is increased, a loading of the spring 57 will occur and then as the applied load is subsequently decreased the stored energy of the spring 57 will be effective on the members 15a and 16a to cause an axial shortening of the device.

Thus upon an increase in the compressive load, the spreading action exerted on the members 15a and 16a by the oppositely sloping bearing surfaces 63 and 64 of the upper part 12a tends to cause sliding of the member 15a on the inclined bearing surface 59 in a downhill direction and sliding of the member 16a along this bearing surface in an uphill direction. Since the downhill sliding movement of the member 15a will take place more readily than the uphill sliding movement of the member 16B, the resultant action is that the member 15EL slides on the bearing surface 59 in a downhill direction while the member 16a remains relatively stationary, thereby causing deflection and loading of the spring 57.

As the compressive load being applied to the device 10a decreases after the engine valve has reached its seated position, as explained above, the energy stored in the spring 57 is relieved, but in order for this to take place the members 15a and 16a must move closer together. For the member 15a to move closer to the member 16a it would need to move along the bearing surface 15 in an uphill direction. Moreover, for the member 15P- to move closer to the member 16a it must push the part 12a upwardly by reason of the cooperative sliding engagement of the inclined bearing surfaces 63 and 65.

On the other hand, the member 16a can move closer to the member 15EL by sliding in a downhill direction along the bearing surface 59. Movement of the member 16a toward the member 15a, however, would require lifting of the upper part 12al through the cooperative sliding engagement of the inclined bearing surfaces 64 and 66. Therefore, since a required lifting of the part 12a during the relative closing movement between the members 15a and 16al is common to both of these members and since a relative closing movement between these mem bers can be accomplished by a downhill movement of the member 16a on the bearing surface 59 as against an uphill movement of the member 15a, the relative closing movement is accomplished through a downhill movement of the member 16a. The relative closing movement between the members 15a and 16a relieves the loading of the spring 57 and since both of the members 15a and 16a have now been moved in a downhill direction along the inclined bearing surface 59 it will be seen that the axial length of the device 10EL has been shortened.

The characteristics of the torsion spring 44 of the lash adjuster 1t), and of the corresponding spring 58 of the analog 10a, are such that this spring has substantially no eect on the downhill movements Of ,ills mem-.vp

bers v151and 16a, that is to say, substantially no eect on the inward movement 'of the nut members 15 and 16 .of Fig. l during the axialshortening of the device While thelatter is under load. On the other hand the characteristics of the springs 44 and 5S are such as to render the spring 44 effective for causing an outward movement of the nut members 15 and 16 when the applied load is relieved, or an uphill movement of the members 15a and 16a of the analog 10a by the spring 58.

The uphill movement imparted to the member 15@ of the analog by the spring 58 upon removal of the applied load is also transmitted through the spring 57 to the member 16a to cause a corresponding uphill movement of the latter member. Similarly in the lash adjuster 14), the spring arms 35 and 36 transmit rotative movement from the inner nut member 15 to the outer nut member 16 in the lengthening direction in response to a lengthening rotative movement imparted to the inner nut member by the torsion spring 44.

From the accompanying drawing and the foregoing detailed description it will now be readily understood that this invention provides a mechanical lash adjuster of a novel form comprising a relatively few number of Vparts and which is not only efficient and durable in character but is relatively compact, such that it can be readily'incorporated in a valve actuating mechanism, preferably by being embodied in a tappet. Y

Although this novel mechanical lash adjuster lhas been illustrated and described herein to a somewhat detailed extent, it will be understood, of course, that the invention is not to be regarded as being limited correspondingly in scope but includes all changes and modifications coming within the terms of the claims hereof.

Having thus described my invention, I claim:

l. In a mechanical lash adjuster, a pair of first and second relatively movable parts adapted to be subjected to load, one of said parts having inclined-plane bearing means thereon and the other of said parts having a plurality of oppositely sloping bearing means thereon, a pair of members each having a iirst follower means engaging said inclined-plane bearing means and a second follower means engaging one of the sloping bearing means of said other part, said members being movable along said inclined-plane bearing means and relative to each other for varying the eifective dimension of said adjuster, and resilient means controlling such movements of said members in response to variations in the applied load.

2. ln a mechanical klash adjuster, a Vpair of irst and second relatively movable parts adapted to be subjected to load, one of said parts having inclined-plane bearing means thereon and the other of said parts having a plurality of oppositely sloping bearing means thereon, a pair of members eachjhaving a rst follower means engaging said inclined-plane bearing means and a second follower means engaging one of the sloping bearing means of said other part, said members being movable along said inclined-plane bearing` means and relative to each other in response to thrust transmitted between said members and said other part through said oppositely sloping bearing means for varying the effective dimension of said adjuster, and resilient means controlling such movements of said members in response to variations in the applied load, said resilient means comprising a first resilient means effective on, one of said members and tending to produce movement thereof along said inclined-plane bearing means in a direction to cause lengthening of said adjuster and a second resilient means effective to transmit actuating force in either direction between said members.

3. In a mechanicalA lash adjuster, a pair of rst and second relatively movable parts adapted to be subjected to load, one of said' parts havingjinclined-plane bearing means thereon andthe other of said parts having a plurality of oppositely sloping bearing means thereon, a pair of members each having a lirst follower means engaging said inclined-piane bearing means and a second follower means engaging one ofthe sloping bearing means 8 of saidother part, said'members being movable along said .inclinedfplane bearing means and relative to each other for varying the effective dimension of said adjuster, a predetermined increase in the applied load being eiective on said members through said oppositely ysloping bearing ,means to apply actuating force to one of :said members in the uphill direction of said inclined-plane hearing means and in the downhill direction to the other of said members with a kresultant downhill movement of t said other member relative to said one member for shortening theieiective dimension of said adjuster, and resilient means controlling such relative .movement between said members'in accordance with the magnitude of the applied load. Y

4. A lash adjuster as deiinedin' claim 3 in which `said resilient means has a double-acting characteristic between said members for transmitting actuating force therebetween in either direction depending upon ywhether the applied load .is increasing or decreasing in magnitude.

5. in a mechanical lash adjuster, a `.pair of substan tially coaxially disposed and relatively axially movable irst and second parts adapted to be subjected to a reciprocative load, one-of said .parts having inclinedplane helical bearing means thereon and the other of said parts having a plurality of oppositely sloping axially inclined bearing means thereon, a pair of members each having a first follower means engaging said helical bearing means and a second follower means engaging one of the Vsloping bearing means. of said other part, said members being rotatably movable along said helical bearing means and relative to 4each other forvarying the etective length of said adjuster, apredetermined increase in the `applied load kbeing keffective Von said members through said oppositely sloping bearing means to apply actuating force to one of said members invan Iuphill direction along said helical bearing means and in a downhill direction ,to the .other of said members witha resultant downhill kmovement of said other member relative to said one member for shortening the effective lengthrof said adjuster, and ktorsion spring means controlling such relative movement between saidmembers in accordance with changes occurring in the magnitude of lthe appliedload.

6. A mechanical `lash adjuster as deiined ink claim 5 in which said torsion .spring means comprises iatirst torsion spring means continuously effective. on said other member in a direction tending to increasethe effective length of said adjuster, and a second torsion spring means effective between said members for transmitting actuating force therebetween in either direction depending upon whether the applied'load is increasing or decreasing in magnitude.

7. ln a variable length lash adjuster, a pair of substantially coaXially extending relatively movable parts adapted to be subjected to a reciprocat'ive load and one of which parts is threaded .and the other of which yhas oppositely sloping inclined wedge elements thereon, and means oper-` atively connecting said parts for causing relative axial movement therebetween in response to variations in the applied load comprising at leastk two individual nut mem bers engaging thethread of saidrone part and having rotative drive connection with said otherY part through the respective inclinedv wedge elements of the latter.

8. In a variable length lash adjuster, a pair of substan# tially coaXially extending relatively ymovableparts adapted to be subjected to a reciprocative/load and one kof which parts is threaded and the other of which has oppositely sloping inclined wedge elements thereon, meansaoperatively connecting said parts for causing relative axial movement therebetween in response to variations in the applied load comprising at least two individual nut meine. bers engaging the thread of said one part and having rotative drive connection withfsaid otherpart through the respective inclined wedge'elements. of the latter, and coupling means etiective between said nut members for controlling relative rotation therebetween.

9..Y in a variable length lash adjuster, a pair of sub1 stantially coaxially extending relatively movable parts adapted to be subjected to a reciprocative load and one of which parts is threaded and the other of which has oppositely sloping inclined wedge elements thereon, means operatively connecting said parts for causing relative axial movement therebetween in response to variations in the applied load comprising at least two individual nut members engaging the thread of said one part and having rotative drive connection with said other parts through the respective inclined wedge elements of the latter, and yieldable torque transmitting means eiective between said nut members for controlling relative rotation therebetween.

10. In a variable length lash adjuster; an axially threaded part; an adjusting unit comprising a substantially coaxial part having oppositely sloping inclined wedge elements thereon, and a pair of nut members threadedly engaging said threaded part and having rotative drive connection with said coaxial part through the respective inclined wedge elements of the latter; resilient means etective on at least one of said nut members in a direction tending to cause lengthening of said adjuster; and rother resilient means torsionally effective between said nut members for controlling relative rotation therebetween.

11. In a variable length lash adjuster; an axially threaded part; an adjusting unit comprising a substantially coaxial part having oppositely sloping spline groups thereon, and a pair of nut members threadedly engaging said threaded part and having rotative drive connection with said coaxial part through the respective spline groups of the latter; and resilient means torsionally eective between said nut members for controlling relative rotation therebetween.

12. In a variable length lash adjuster; an axially threaded part; an adjusting unit comprising a substantially coaxial part having oppositely sloping inclined wedge elements thereon, and a pair of nut members threadedly engaging said threaded part and having rotative drive connection with said coaxial part through the respective inclined wedge elements of the latter; torsional resilient means rotatively effective on at least one of said nut members in a direction tending to cause lengthening of said adjuster; and other resilient means torsionally effective between said nut members in response to relative rotation between the nut members for controlling such relative rotation of the nut members.

13. In a variable length lash adjuster, first and second coaxially disposed parts adapted to be subjected to reciprocative loading, one of said parts being an axially threaded body and the other part having oppositely inclined spline groups thereon, a pair of nut members threadedly engaging said threaded body and having rotative drive connection with said other part through the respective spline groups of the latter, and resilient torsional means eiective to cause rotative movement of said nut members for producing length variations in said adjuster in response to variations in the applied load.

14. In a mechanical lash adjuster, a pair of rst and second relatively movable parts adapted to be subjected to load, one of said parts having inclined-plane bearing means thereon and the other of said parts having a plurality of oppositely sloping bearing means thereon, a pair of members each having a first follower means engaging said inclined-plane bearing means and a second follower means engaging one ofthe sloping bearing means of said other part, said members being movable along said inclined-plane bearing means and relative to each other for varying the etective dimension of said adjuster, and resilient means controlling such movements of said members in response to variations in the applied load inclining spring means of the cantilever type eective between said members.

l5. In a variable length lash adjuster, iirst and second coaxially disposed parts adapted to be subjected to reciprocative loading, one of said parts being an axially threaded body and the other part having oppositely inclined spline groups thereon, a pair of nut members threadedly engaging said threaded body and having rotative drive connection with said other part through the respective spline groups of the latter, and resilient torsional means etective to cause rotative movement of said nut members for producing length variations in said adjuster in response to variations in the applied load including spring means of the cantilever type eiective between said nut members.

16. In a variable length lash adjuster, rst and second coaxially disposed parts adapted to be subjected to reciprocative loading, one of said parts being an axially threaded body and the other part having oppositely inclined spline groups thereon, a pair of nut members threadedly engaging said threaded body and having rotative drive connection with said other part through the respective spline groups of the latter, one of said nut members having anuularly spaced recesses therein, and yieldable arms carried by the other nut member and engaging in said recesses, said arms being torsionally elective between said nut members in producing length variations in said adjuster in response to variations in the applied load.

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